Has it happened multiple times? I would try booting into option mode (hold down the option key instead of "C") and see if that makes a difference.
I'd try removing expansion RAM, Airport, and battery, and then reset the PMU and PRAM, and try again.
If that doesn't work, I'd probably open the machine back up and check for loose connections and loose screws bouncing around inside. It sounds as if the computer is crashing, and I've seen things like that happen from a loose screw shorting out the logic board...you might want to try shaking it lightly to see if you hear screws rattling around inside.